Nitrogen addition significantly affects soil aggregate stability by altering the aggregate microenvironment. Although the ecological effects of nitrogen addition on soil aggregates have been extensively investigated, studies specifically focusing on the responses of soil aggregate stability in Larix olgensis forest understories remain scarce. The effects of different forms of nitrogen addition (urea (CO(NH2)2), ammonium chloride (NH4Cl), and sodium nitrate (NaNO3)) were investigated at 20 kg N·ha−1·yr−1 across all treatments, and the physicochemical properties, stability, and microbial community composition of soil aggregates were determined to analyze soil aggregate stability. NaNO3 significantly increased soil nutrient contents, promoted the formation of macroaggregates, and significantly enhanced soil aggregate stability. NH4Cl significantly decreased bacterial diversity in microaggregates, while NaNO3 significantly elevated fungal diversity in macroaggregates. CO(NH2)2 and NH4Cl increased the relative abundances of Ascomycota and Proteobacteria in microaggregates, whereas NaNO3 elevated the relative abundances of Mortierellomycota and Gemmatimonadetes in soil aggregates of all particle sizes. These results indicated that NaNO3 was more effective in improving soil aggregate stability and exerted regulatory effects on microbial community structure compared to the other nitrogen forms. These findings can provide a theoretical basis for an in-depth understanding of the microecological processes of forest soil aggregates under the context of nitrogen deposition.
Qu et al. (Sun,) studied this question.